SAFE public projects git trees. - safe/jmp/linux-2.6/blob - arch/um/drivers/ubd_kern.c

   1 /*
   2  * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 /* 2001-09-28...2002-04-17
   7  * Partition stuff by James_McMechan@hotmail.com
   8  * old style ubd by setting UBD_SHIFT to 0
   9  * 2002-09-27...2002-10-18 massive tinkering for 2.5
  10  * partitions have changed in 2.5
  11  * 2003-01-29 more tinkering for 2.5.59-1
  12  * This should now address the sysfs problems and has
  13  * the symlink for devfs to allow for booting with
  14  * the common /dev/ubd/discX/... names rather than
  15  * only /dev/ubdN/discN this version also has lots of
  16  * clean ups preparing for ubd-many.
  17  * James McMechan
  18  */
  19
  20 #define MAJOR_NR UBD_MAJOR
  21 #define UBD_SHIFT 4
  22
  23 #include "linux/module.h"
  24 #include "linux/blkdev.h"
  25 #include "linux/hdreg.h"
  26 #include "linux/init.h"
  27 #include "linux/cdrom.h"
  28 #include "linux/proc_fs.h"
  29 #include "linux/ctype.h"
  30 #include "linux/capability.h"
  31 #include "linux/mm.h"
  32 #include "linux/vmalloc.h"
  33 #include "linux/blkpg.h"
  34 #include "linux/genhd.h"
  35 #include "linux/spinlock.h"
  36 #include "linux/platform_device.h"
  37 #include "asm/segment.h"
  38 #include "asm/uaccess.h"
  39 #include "asm/irq.h"
  40 #include "asm/types.h"
  41 #include "asm/tlbflush.h"
  42 #include "user_util.h"
  43 #include "mem_user.h"
  44 #include "kern_util.h"
  45 #include "kern.h"
  46 #include "mconsole_kern.h"
  47 #include "init.h"
  48 #include "irq_user.h"
  49 #include "irq_kern.h"
  50 #include "ubd_user.h"
  51 #include "os.h"
  52 #include "mem.h"
  53 #include "mem_kern.h"
  54 #include "cow.h"
  55
  56 enum ubd_req { UBD_READ, UBD_WRITE };
  57
  58 struct io_thread_req {
  59         enum ubd_req op;
  60         int fds[2];
  61         unsigned long offsets[2];
  62         unsigned long long offset;
  63         unsigned long length;
  64         char *buffer;
  65         int sectorsize;
  66         unsigned long sector_mask;
  67         unsigned long long cow_offset;
  68         unsigned long bitmap_words[2];
  69         int error;
  70 };
  71
  72 extern int open_ubd_file(char *file, struct openflags *openflags, int shared,
  73                          char **backing_file_out, int *bitmap_offset_out,
  74                          unsigned long *bitmap_len_out, int *data_offset_out,
  75                          int *create_cow_out);
  76 extern int create_cow_file(char *cow_file, char *backing_file,
  77                            struct openflags flags, int sectorsize,
  78                            int alignment, int *bitmap_offset_out,
  79                            unsigned long *bitmap_len_out,
  80                            int *data_offset_out);
  81 extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
  82 extern void do_io(struct io_thread_req *req);
  83
  84 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
  85 {
  86         __u64 n;
  87         int bits, off;
  88
  89         bits = sizeof(data[0]) * 8;
  90         n = bit / bits;
  91         off = bit % bits;
  92         return((data[n] & (1 << off)) != 0);
  93 }
  94
  95 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
  96 {
  97         __u64 n;
  98         int bits, off;
  99
 100         bits = sizeof(data[0]) * 8;
 101         n = bit / bits;
 102         off = bit % bits;
 103         data[n] |= (1 << off);
 104 }
 105 /*End stuff from ubd_user.h*/
 106
 107 #define DRIVER_NAME "uml-blkdev"
 108
 109 /* Can be taken in interrupt context, and is passed to the block layer to lock
 110  * the request queue. Kernel side code knows that. */
 111 static DEFINE_SPINLOCK(ubd_io_lock);
 112
 113 static DEFINE_MUTEX(ubd_lock);
 114
 115 /* XXX - this made sense in 2.4 days, now it's only used as a boolean, and
 116  * probably it doesn't make sense even for that. */
 117 static int do_ubd;
 118
 119 static int ubd_open(struct inode * inode, struct file * filp);
 120 static int ubd_release(struct inode * inode, struct file * file);
 121 static int ubd_ioctl(struct inode * inode, struct file * file,
 122                      unsigned int cmd, unsigned long arg);
 123 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
 124
 125 #define MAX_DEV (16)
 126
 127 static struct block_device_operations ubd_blops = {
 128         .owner          = THIS_MODULE,
 129         .open           = ubd_open,
 130         .release        = ubd_release,
 131         .ioctl          = ubd_ioctl,
 132         .getgeo         = ubd_getgeo,
 133 };
 134
 135 /* Protected by the queue_lock */
 136 static request_queue_t *ubd_queue;
 137
 138 /* Protected by ubd_lock */
 139 static int fake_major = MAJOR_NR;
 140
 141 static struct gendisk *ubd_gendisk[MAX_DEV];
 142 static struct gendisk *fake_gendisk[MAX_DEV];
 143
 144 #ifdef CONFIG_BLK_DEV_UBD_SYNC
 145 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
 146                                          .cl = 1 })
 147 #else
 148 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
 149                                          .cl = 1 })
 150 #endif
 151
 152 /* Not protected - changed only in ubd_setup_common and then only to
 153  * to enable O_SYNC.
 154  */
 155 static struct openflags global_openflags = OPEN_FLAGS;
 156
 157 struct cow {
 158         /* backing file name */
 159         char *file;
 160         /* backing file fd */
 161         int fd;
 162         unsigned long *bitmap;
 163         unsigned long bitmap_len;
 164         int bitmap_offset;
 165         int data_offset;
 166 };
 167
 168 struct ubd {
 169         /* name (and fd, below) of the file opened for writing, either the
 170          * backing or the cow file. */
 171         char *file;
 172         int count;
 173         int fd;
 174         __u64 size;
 175         struct openflags boot_openflags;
 176         struct openflags openflags;
 177         unsigned shared:1;
 178         unsigned no_cow:1;
 179         struct cow cow;
 180         struct platform_device pdev;
 181 };
 182
 183 #define DEFAULT_COW { \
 184         .file =                 NULL, \
 185         .fd =                   -1, \
 186         .bitmap =               NULL, \
 187         .bitmap_offset =        0, \
 188         .data_offset =          0, \
 189 }
 190
 191 #define DEFAULT_UBD { \
 192         .file =                 NULL, \
 193         .count =                0, \
 194         .fd =                   -1, \
 195         .size =                 -1, \
 196         .boot_openflags =       OPEN_FLAGS, \
 197         .openflags =            OPEN_FLAGS, \
 198         .no_cow =               0, \
 199         .shared =               0, \
 200         .cow =                  DEFAULT_COW, \
 201 }
 202
 203 struct ubd ubd_devs[MAX_DEV] = { [ 0 ... MAX_DEV - 1 ] = DEFAULT_UBD };
 204
 205 /* Only changed by fake_ide_setup which is a setup */
 206 static int fake_ide = 0;
 207 static struct proc_dir_entry *proc_ide_root = NULL;
 208 static struct proc_dir_entry *proc_ide = NULL;
 209
 210 static void make_proc_ide(void)
 211 {
 212         proc_ide_root = proc_mkdir("ide", NULL);
 213         proc_ide = proc_mkdir("ide0", proc_ide_root);
 214 }
 215
 216 static int proc_ide_read_media(char *page, char **start, off_t off, int count,
 217                                int *eof, void *data)
 218 {
 219         int len;
 220
 221         strcpy(page, "disk\n");
 222         len = strlen("disk\n");
 223         len -= off;
 224         if (len < count){
 225                 *eof = 1;
 226                 if (len <= 0) return 0;
 227         }
 228         else len = count;
 229         *start = page + off;
 230         return len;
 231 }
 232
 233 static void make_ide_entries(char *dev_name)
 234 {
 235         struct proc_dir_entry *dir, *ent;
 236         char name[64];
 237
 238         if(proc_ide_root == NULL) make_proc_ide();
 239
 240         dir = proc_mkdir(dev_name, proc_ide);
 241         if(!dir) return;
 242
 243         ent = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
 244         if(!ent) return;
 245         ent->nlink = 1;
 246         ent->data = NULL;
 247         ent->read_proc = proc_ide_read_media;
 248         ent->write_proc = NULL;
 249         sprintf(name,"ide0/%s", dev_name);
 250         proc_symlink(dev_name, proc_ide_root, name);
 251 }
 252
 253 static int fake_ide_setup(char *str)
 254 {
 255         fake_ide = 1;
 256         return(1);
 257 }
 258
 259 __setup("fake_ide", fake_ide_setup);
 260
 261 __uml_help(fake_ide_setup,
 262 "fake_ide\n"
 263 "    Create ide0 entries that map onto ubd devices.\n\n"
 264 );
 265
 266 static int parse_unit(char **ptr)
 267 {
 268         char *str = *ptr, *end;
 269         int n = -1;
 270
 271         if(isdigit(*str)) {
 272                 n = simple_strtoul(str, &end, 0);
 273                 if(end == str)
 274                         return(-1);
 275                 *ptr = end;
 276         }
 277         else if (('a' <= *str) && (*str <= 'z')) {
 278                 n = *str - 'a';
 279                 str++;
 280                 *ptr = str;
 281         }
 282         return(n);
 283 }
 284
 285 /* If *index_out == -1 at exit, the passed option was a general one;
 286  * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
 287  * should not be freed on exit.
 288  */
 289 static int ubd_setup_common(char *str, int *index_out, char **error_out)
 290 {
 291         struct ubd *ubd_dev;
 292         struct openflags flags = global_openflags;
 293         char *backing_file;
 294         int n, err, i;
 295
 296         if(index_out) *index_out = -1;
 297         n = *str;
 298         if(n == '='){
 299                 char *end;
 300                 int major;
 301
 302                 str++;
 303                 if(!strcmp(str, "sync")){
 304                         global_openflags = of_sync(global_openflags);
 305                         return 0;
 306                 }
 307                 major = simple_strtoul(str, &end, 0);
 308                 if((*end != '\0') || (end == str)){
 309                         *error_out = "Didn't parse major number";
 310                         return -EINVAL;
 311                 }
 312
 313                 err = -EINVAL;
 314                 mutex_lock(&ubd_lock);
 315                 if(fake_major != MAJOR_NR){
 316                         *error_out = "Can't assign a fake major twice";
 317                         goto out1;
 318                 }
 319
 320                 fake_major = major;
 321
 322                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
 323                        major);
 324                 err = 0;
 325         out1:
 326                 mutex_unlock(&ubd_lock);
 327                 return err;
 328         }
 329
 330         n = parse_unit(&str);
 331         if(n < 0){
 332                 *error_out = "Couldn't parse device number";
 333                 return -EINVAL;
 334         }
 335         if(n >= MAX_DEV){
 336                 *error_out = "Device number out of range";
 337                 return 1;
 338         }
 339
 340         err = -EBUSY;
 341         mutex_lock(&ubd_lock);
 342
 343         ubd_dev = &ubd_devs[n];
 344         if(ubd_dev->file != NULL){
 345                 *error_out = "Device is already configured";
 346                 goto out;
 347         }
 348
 349         if (index_out)
 350                 *index_out = n;
 351
 352         err = -EINVAL;
 353         for (i = 0; i < sizeof("rscd="); i++) {
 354                 switch (*str) {
 355                 case 'r':
 356                         flags.w = 0;
 357                         break;
 358                 case 's':
 359                         flags.s = 1;
 360                         break;
 361                 case 'd':
 362                         ubd_dev->no_cow = 1;
 363                         break;
 364                 case 'c':
 365                         ubd_dev->shared = 1;
 366                         break;
 367                 case '=':
 368                         str++;
 369                         goto break_loop;
 370                 default:
 371                         *error_out = "Expected '=' or flag letter "
 372                                 "(r, s, c, or d)";
 373                         goto out;
 374                 }
 375                 str++;
 376         }
 377
 378         if (*str == '=')
 379                 *error_out = "Too many flags specified";
 380         else
 381                 *error_out = "Missing '='";
 382         goto out;
 383
 384 break_loop:
 385         backing_file = strchr(str, ',');
 386
 387         if (backing_file == NULL)
 388                 backing_file = strchr(str, ':');
 389
 390         if(backing_file != NULL){
 391                 if(ubd_dev->no_cow){
 392                         *error_out = "Can't specify both 'd' and a cow file";
 393                         goto out;
 394                 }
 395                 else {
 396                         *backing_file = '\0';
 397                         backing_file++;
 398                 }
 399         }
 400         err = 0;
 401         ubd_dev->file = str;
 402         ubd_dev->cow.file = backing_file;
 403         ubd_dev->boot_openflags = flags;
 404 out:
 405         mutex_unlock(&ubd_lock);
 406         return err;
 407 }
 408
 409 static int ubd_setup(char *str)
 410 {
 411         char *error;
 412         int err;
 413
 414         err = ubd_setup_common(str, NULL, &error);
 415         if(err)
 416                 printk(KERN_ERR "Failed to initialize device with \"%s\" : "
 417                        "%s\n", str, error);
 418         return 1;
 419 }
 420
 421 __setup("ubd", ubd_setup);
 422 __uml_help(ubd_setup,
 423 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
 424 "    This is used to associate a device with a file in the underlying\n"
 425 "    filesystem. When specifying two filenames, the first one is the\n"
 426 "    COW name and the second is the backing file name. As separator you can\n"
 427 "    use either a ':' or a ',': the first one allows writing things like;\n"
 428 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
 429 "    while with a ',' the shell would not expand the 2nd '~'.\n"
 430 "    When using only one filename, UML will detect whether to treat it like\n"
 431 "    a COW file or a backing file. To override this detection, add the 'd'\n"
 432 "    flag:\n"
 433 "       ubd0d=BackingFile\n"
 434 "    Usually, there is a filesystem in the file, but \n"
 435 "    that's not required. Swap devices containing swap files can be\n"
 436 "    specified like this. Also, a file which doesn't contain a\n"
 437 "    filesystem can have its contents read in the virtual \n"
 438 "    machine by running 'dd' on the device. <n> must be in the range\n"
 439 "    0 to 7. Appending an 'r' to the number will cause that device\n"
 440 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
 441 "    an 's' will cause data to be written to disk on the host immediately.\n\n"
 442 );
 443
 444 static int udb_setup(char *str)
 445 {
 446         printk("udb%s specified on command line is almost certainly a ubd -> "
 447                "udb TYPO\n", str);
 448         return(1);
 449 }
 450
 451 __setup("udb", udb_setup);
 452 __uml_help(udb_setup,
 453 "udb\n"
 454 "    This option is here solely to catch ubd -> udb typos, which can be\n"
 455 "    to impossible to catch visually unless you specifically look for\n"
 456 "    them.  The only result of any option starting with 'udb' is an error\n"
 457 "    in the boot output.\n\n"
 458 );
 459
 460 static int fakehd_set = 0;
 461 static int fakehd(char *str)
 462 {
 463         printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
 464         fakehd_set = 1;
 465         return 1;
 466 }
 467
 468 __setup("fakehd", fakehd);
 469 __uml_help(fakehd,
 470 "fakehd\n"
 471 "    Change the ubd device name to \"hd\".\n\n"
 472 );
 473
 474 static void do_ubd_request(request_queue_t * q);
 475
 476 /* Only changed by ubd_init, which is an initcall. */
 477 int thread_fd = -1;
 478
 479 /* Changed by ubd_handler, which is serialized because interrupts only
 480  * happen on CPU 0.
 481  * XXX: currently unused.
 482  */
 483 static int intr_count = 0;
 484
 485 /* call ubd_finish if you need to serialize */
 486 static void __ubd_finish(struct request *req, int error)
 487 {
 488         int nsect;
 489
 490         if(error){
 491                 end_request(req, 0);
 492                 return;
 493         }
 494         nsect = req->current_nr_sectors;
 495         req->sector += nsect;
 496         req->buffer += nsect << 9;
 497         req->errors = 0;
 498         req->nr_sectors -= nsect;
 499         req->current_nr_sectors = 0;
 500         end_request(req, 1);
 501 }
 502
 503 /* Callable only from interrupt context - otherwise you need to do
 504  * spin_lock_irq()/spin_lock_irqsave() */
 505 static inline void ubd_finish(struct request *req, int error)
 506 {
 507         spin_lock(&ubd_io_lock);
 508         __ubd_finish(req, error);
 509         spin_unlock(&ubd_io_lock);
 510 }
 511
 512 /* XXX - move this inside ubd_intr. */
 513 /* Called without ubd_io_lock held, and only in interrupt context. */
 514 static void ubd_handler(void)
 515 {
 516         struct io_thread_req req;
 517         struct request *rq = elv_next_request(ubd_queue);
 518         int n;
 519
 520         do_ubd = 0;
 521         intr_count++;
 522         n = os_read_file(thread_fd, &req, sizeof(req));
 523         if(n != sizeof(req)){
 524                 printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
 525                        "err = %d\n", os_getpid(), -n);
 526                 spin_lock(&ubd_io_lock);
 527                 end_request(rq, 0);
 528                 spin_unlock(&ubd_io_lock);
 529                 return;
 530         }
 531
 532         ubd_finish(rq, req.error);
 533         reactivate_fd(thread_fd, UBD_IRQ);
 534         spin_lock(&ubd_io_lock);
 535         do_ubd_request(ubd_queue);
 536         spin_unlock(&ubd_io_lock);
 537 }
 538
 539 static irqreturn_t ubd_intr(int irq, void *dev)
 540 {
 541         ubd_handler();
 542         return(IRQ_HANDLED);
 543 }
 544
 545 /* Only changed by ubd_init, which is an initcall. */
 546 static int io_pid = -1;
 547
 548 void kill_io_thread(void)
 549 {
 550         if(io_pid != -1)
 551                 os_kill_process(io_pid, 1);
 552 }
 553
 554 __uml_exitcall(kill_io_thread);
 555
 556 static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
 557 {
 558         char *file;
 559
 560         file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
 561         return(os_file_size(file, size_out));
 562 }
 563
 564 static void ubd_close_dev(struct ubd *ubd_dev)
 565 {
 566         os_close_file(ubd_dev->fd);
 567         if(ubd_dev->cow.file == NULL)
 568                 return;
 569
 570         os_close_file(ubd_dev->cow.fd);
 571         vfree(ubd_dev->cow.bitmap);
 572         ubd_dev->cow.bitmap = NULL;
 573 }
 574
 575 static int ubd_open_dev(struct ubd *ubd_dev)
 576 {
 577         struct openflags flags;
 578         char **back_ptr;
 579         int err, create_cow, *create_ptr;
 580         int fd;
 581
 582         ubd_dev->openflags = ubd_dev->boot_openflags;
 583         create_cow = 0;
 584         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
 585         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
 586
 587         fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
 588                                 back_ptr, &ubd_dev->cow.bitmap_offset,
 589                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
 590                                 create_ptr);
 591
 592         if((fd == -ENOENT) && create_cow){
 593                 fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
 594                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
 595                                           &ubd_dev->cow.bitmap_offset,
 596                                           &ubd_dev->cow.bitmap_len,
 597                                           &ubd_dev->cow.data_offset);
 598                 if(fd >= 0){
 599                         printk(KERN_INFO "Creating \"%s\" as COW file for "
 600                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
 601                 }
 602         }
 603
 604         if(fd < 0){
 605                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
 606                        -fd);
 607                 return fd;
 608         }
 609         ubd_dev->fd = fd;
 610
 611         if(ubd_dev->cow.file != NULL){
 612                 err = -ENOMEM;
 613                 ubd_dev->cow.bitmap = (void *) vmalloc(ubd_dev->cow.bitmap_len);
 614                 if(ubd_dev->cow.bitmap == NULL){
 615                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
 616                         goto error;
 617                 }
 618                 flush_tlb_kernel_vm();
 619
 620                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
 621                                       ubd_dev->cow.bitmap_offset,
 622                                       ubd_dev->cow.bitmap_len);
 623                 if(err < 0)
 624                         goto error;
 625
 626                 flags = ubd_dev->openflags;
 627                 flags.w = 0;
 628                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
 629                                     NULL, NULL, NULL, NULL);
 630                 if(err < 0) goto error;
 631                 ubd_dev->cow.fd = err;
 632         }
 633         return(0);
 634  error:
 635         os_close_file(ubd_dev->fd);
 636         return(err);
 637 }
 638
 639 static int ubd_disk_register(int major, u64 size, int unit,
 640                         struct gendisk **disk_out)
 641
 642 {
 643         struct gendisk *disk;
 644
 645         disk = alloc_disk(1 << UBD_SHIFT);
 646         if(disk == NULL)
 647                 return(-ENOMEM);
 648
 649         disk->major = major;
 650         disk->first_minor = unit << UBD_SHIFT;
 651         disk->fops = &ubd_blops;
 652         set_capacity(disk, size / 512);
 653         if(major == MAJOR_NR)
 654                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
 655         else
 656                 sprintf(disk->disk_name, "ubd_fake%d", unit);
 657
 658         /* sysfs register (not for ide fake devices) */
 659         if (major == MAJOR_NR) {
 660                 ubd_devs[unit].pdev.id   = unit;
 661                 ubd_devs[unit].pdev.name = DRIVER_NAME;
 662                 platform_device_register(&ubd_devs[unit].pdev);
 663                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
 664         }
 665
 666         disk->private_data = &ubd_devs[unit];
 667         disk->queue = ubd_queue;
 668         add_disk(disk);
 669
 670         *disk_out = disk;
 671         return 0;
 672 }
 673
 674 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
 675
 676 static int ubd_add(int n, char **error_out)
 677 {
 678         struct ubd *ubd_dev = &ubd_devs[n];
 679         int err = 0;
 680
 681         if(ubd_dev->file == NULL)
 682                 goto out;
 683
 684         err = ubd_file_size(ubd_dev, &ubd_dev->size);
 685         if(err < 0){
 686                 *error_out = "Couldn't determine size of device's file";
 687                 goto out;
 688         }
 689
 690         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 691
 692         err = ubd_disk_register(MAJOR_NR, ubd_dev->size, n, &ubd_gendisk[n]);
 693         if(err)
 694                 goto out;
 695
 696         if(fake_major != MAJOR_NR)
 697                 ubd_disk_register(fake_major, ubd_dev->size, n,
 698                              &fake_gendisk[n]);
 699
 700         /* perhaps this should also be under the "if (fake_major)" above */
 701         /* using the fake_disk->disk_name and also the fakehd_set name */
 702         if (fake_ide)
 703                 make_ide_entries(ubd_gendisk[n]->disk_name);
 704
 705         err = 0;
 706 out:
 707         return err;
 708 }
 709
 710 static int ubd_config(char *str, char **error_out)
 711 {
 712         int n, ret;
 713
 714         /* This string is possibly broken up and stored, so it's only
 715          * freed if ubd_setup_common fails, or if only general options
 716          * were set.
 717          */
 718         str = kstrdup(str, GFP_KERNEL);
 719         if (str == NULL) {
 720                 *error_out = "Failed to allocate memory";
 721                 return -ENOMEM;
 722         }
 723
 724         ret = ubd_setup_common(str, &n, error_out);
 725         if (ret)
 726                 goto err_free;
 727
 728         if (n == -1) {
 729                 ret = 0;
 730                 goto err_free;
 731         }
 732
 733         mutex_lock(&ubd_lock);
 734         ret = ubd_add(n, error_out);
 735         if (ret)
 736                 ubd_devs[n].file = NULL;
 737         mutex_unlock(&ubd_lock);
 738
 739 out:
 740         return ret;
 741
 742 err_free:
 743         kfree(str);
 744         goto out;
 745 }
 746
 747 static int ubd_get_config(char *name, char *str, int size, char **error_out)
 748 {
 749         struct ubd *ubd_dev;
 750         int n, len = 0;
 751
 752         n = parse_unit(&name);
 753         if((n >= MAX_DEV) || (n < 0)){
 754                 *error_out = "ubd_get_config : device number out of range";
 755                 return(-1);
 756         }
 757
 758         ubd_dev = &ubd_devs[n];
 759         mutex_lock(&ubd_lock);
 760
 761         if(ubd_dev->file == NULL){
 762                 CONFIG_CHUNK(str, size, len, "", 1);
 763                 goto out;
 764         }
 765
 766         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
 767
 768         if(ubd_dev->cow.file != NULL){
 769                 CONFIG_CHUNK(str, size, len, ",", 0);
 770                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
 771         }
 772         else CONFIG_CHUNK(str, size, len, "", 1);
 773
 774  out:
 775         mutex_unlock(&ubd_lock);
 776         return(len);
 777 }
 778
 779 static int ubd_id(char **str, int *start_out, int *end_out)
 780 {
 781         int n;
 782
 783         n = parse_unit(str);
 784         *start_out = 0;
 785         *end_out = MAX_DEV - 1;
 786         return n;
 787 }
 788
 789 static int ubd_remove(int n, char **error_out)
 790 {
 791         struct ubd *ubd_dev;
 792         int err = -ENODEV;
 793
 794         mutex_lock(&ubd_lock);
 795
 796         if(ubd_gendisk[n] == NULL)
 797                 goto out;
 798
 799         ubd_dev = &ubd_devs[n];
 800
 801         if(ubd_dev->file == NULL)
 802                 goto out;
 803
 804         /* you cannot remove a open disk */
 805         err = -EBUSY;
 806         if(ubd_dev->count > 0)
 807                 goto out;
 808
 809         del_gendisk(ubd_gendisk[n]);
 810         put_disk(ubd_gendisk[n]);
 811         ubd_gendisk[n] = NULL;
 812
 813         if(fake_gendisk[n] != NULL){
 814                 del_gendisk(fake_gendisk[n]);
 815                 put_disk(fake_gendisk[n]);
 816                 fake_gendisk[n] = NULL;
 817         }
 818
 819         platform_device_unregister(&ubd_dev->pdev);
 820         *ubd_dev = ((struct ubd) DEFAULT_UBD);
 821         err = 0;
 822 out:
 823         mutex_unlock(&ubd_lock);
 824         return err;
 825 }
 826
 827 /* All these are called by mconsole in process context and without
 828  * ubd-specific locks.
 829  */
 830 static struct mc_device ubd_mc = {
 831         .list           = LIST_HEAD_INIT(ubd_mc.list),
 832         .name           = "ubd",
 833         .config         = ubd_config,
 834         .get_config     = ubd_get_config,
 835         .id             = ubd_id,
 836         .remove         = ubd_remove,
 837 };
 838
 839 static int __init ubd_mc_init(void)
 840 {
 841         mconsole_register_dev(&ubd_mc);
 842         return 0;
 843 }
 844
 845 __initcall(ubd_mc_init);
 846
 847 static int __init ubd0_init(void)
 848 {
 849         struct ubd *ubd_dev = &ubd_devs[0];
 850
 851         if(ubd_dev->file == NULL)
 852                 ubd_dev->file = "root_fs";
 853         return(0);
 854 }
 855
 856 __initcall(ubd0_init);
 857
 858 static struct platform_driver ubd_driver = {
 859         .driver = {
 860                 .name  = DRIVER_NAME,
 861         },
 862 };
 863
 864 static int __init ubd_init(void)
 865 {
 866         char *error;
 867         int i, err;
 868
 869         if (register_blkdev(MAJOR_NR, "ubd"))
 870                 return -1;
 871
 872         ubd_queue = blk_init_queue(do_ubd_request, &ubd_io_lock);
 873         if (!ubd_queue) {
 874                 unregister_blkdev(MAJOR_NR, "ubd");
 875                 return -1;
 876         }
 877
 878         if (fake_major != MAJOR_NR) {
 879                 char name[sizeof("ubd_nnn\0")];
 880
 881                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
 882                 if (register_blkdev(fake_major, "ubd"))
 883                         return -1;
 884         }
 885         platform_driver_register(&ubd_driver);
 886         for (i = 0; i < MAX_DEV; i++){
 887                 err = ubd_add(i, &error);
 888                 if(err)
 889                         printk(KERN_ERR "Failed to initialize ubd device %d :"
 890                                "%s\n", i, error);
 891         }
 892         return 0;
 893 }
 894
 895 late_initcall(ubd_init);
 896
 897 static int __init ubd_driver_init(void){
 898         unsigned long stack;
 899         int err;
 900
 901         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
 902         if(global_openflags.s){
 903                 printk(KERN_INFO "ubd: Synchronous mode\n");
 904                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
 905                  * enough. So use anyway the io thread. */
 906         }
 907         stack = alloc_stack(0, 0);
 908         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
 909                                  &thread_fd);
 910         if(io_pid < 0){
 911                 printk(KERN_ERR
 912                        "ubd : Failed to start I/O thread (errno = %d) - "
 913                        "falling back to synchronous I/O\n", -io_pid);
 914                 io_pid = -1;
 915                 return(0);
 916         }
 917         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
 918                              IRQF_DISABLED, "ubd", ubd_devs);
 919         if(err != 0)
 920                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
 921         return 0;
 922 }
 923
 924 device_initcall(ubd_driver_init);
 925
 926 static int ubd_open(struct inode *inode, struct file *filp)
 927 {
 928         struct gendisk *disk = inode->i_bdev->bd_disk;
 929         struct ubd *ubd_dev = disk->private_data;
 930         int err = 0;
 931
 932         if(ubd_dev->count == 0){
 933                 err = ubd_open_dev(ubd_dev);
 934                 if(err){
 935                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
 936                                disk->disk_name, ubd_dev->file, -err);
 937                         goto out;
 938                 }
 939         }
 940         ubd_dev->count++;
 941         set_disk_ro(disk, !ubd_dev->openflags.w);
 942
 943         /* This should no more be needed. And it didn't work anyway to exclude
 944          * read-write remounting of filesystems.*/
 945         /*if((filp->f_mode & FMODE_WRITE) && !ubd_dev->openflags.w){
 946                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
 947                 err = -EROFS;
 948         }*/
 949  out:
 950         return(err);
 951 }
 952
 953 static int ubd_release(struct inode * inode, struct file * file)
 954 {
 955         struct gendisk *disk = inode->i_bdev->bd_disk;
 956         struct ubd *ubd_dev = disk->private_data;
 957
 958         if(--ubd_dev->count == 0)
 959                 ubd_close_dev(ubd_dev);
 960         return(0);
 961 }
 962
 963 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
 964                           __u64 *cow_offset, unsigned long *bitmap,
 965                           __u64 bitmap_offset, unsigned long *bitmap_words,
 966                           __u64 bitmap_len)
 967 {
 968         __u64 sector = io_offset >> 9;
 969         int i, update_bitmap = 0;
 970
 971         for(i = 0; i < length >> 9; i++){
 972                 if(cow_mask != NULL)
 973                         ubd_set_bit(i, (unsigned char *) cow_mask);
 974                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
 975                         continue;
 976
 977                 update_bitmap = 1;
 978                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
 979         }
 980
 981         if(!update_bitmap)
 982                 return;
 983
 984         *cow_offset = sector / (sizeof(unsigned long) * 8);
 985
 986         /* This takes care of the case where we're exactly at the end of the
 987          * device, and *cow_offset + 1 is off the end.  So, just back it up
 988          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
 989          * for the original diagnosis.
 990          */
 991         if(*cow_offset == ((bitmap_len + sizeof(unsigned long) - 1) /
 992                            sizeof(unsigned long) - 1))
 993                 (*cow_offset)--;
 994
 995         bitmap_words[0] = bitmap[*cow_offset];
 996         bitmap_words[1] = bitmap[*cow_offset + 1];
 997
 998         *cow_offset *= sizeof(unsigned long);
 999         *cow_offset += bitmap_offset;
1000 }
1001
1002 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
1003                        __u64 bitmap_offset, __u64 bitmap_len)
1004 {
1005         __u64 sector = req->offset >> 9;
1006         int i;
1007
1008         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
1009                 panic("Operation too long");
1010
1011         if(req->op == UBD_READ) {
1012                 for(i = 0; i < req->length >> 9; i++){
1013                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1014                                 ubd_set_bit(i, (unsigned char *)
1015                                             &req->sector_mask);
1016                 }
1017         }
1018         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
1019                            &req->cow_offset, bitmap, bitmap_offset,
1020                            req->bitmap_words, bitmap_len);
1021 }
1022
1023 /* Called with ubd_io_lock held */
1024 static int prepare_request(struct request *req, struct io_thread_req *io_req)
1025 {
1026         struct gendisk *disk = req->rq_disk;
1027         struct ubd *ubd_dev = disk->private_data;
1028         __u64 offset;
1029         int len;
1030
1031         /* This should be impossible now */
1032         if((rq_data_dir(req) == WRITE) && !ubd_dev->openflags.w){
1033                 printk("Write attempted on readonly ubd device %s\n",
1034                        disk->disk_name);
1035                 end_request(req, 0);
1036                 return(1);
1037         }
1038
1039         offset = ((__u64) req->sector) << 9;
1040         len = req->current_nr_sectors << 9;
1041
1042         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd : ubd_dev->fd;
1043         io_req->fds[1] = ubd_dev->fd;
1044         io_req->cow_offset = -1;
1045         io_req->offset = offset;
1046         io_req->length = len;
1047         io_req->error = 0;
1048         io_req->sector_mask = 0;
1049
1050         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1051         io_req->offsets[0] = 0;
1052         io_req->offsets[1] = ubd_dev->cow.data_offset;
1053         io_req->buffer = req->buffer;
1054         io_req->sectorsize = 1 << 9;
1055
1056         if(ubd_dev->cow.file != NULL)
1057                 cowify_req(io_req, ubd_dev->cow.bitmap, ubd_dev->cow.bitmap_offset,
1058                            ubd_dev->cow.bitmap_len);
1059
1060         return(0);
1061 }
1062
1063 /* Called with ubd_io_lock held */
1064 static void do_ubd_request(request_queue_t *q)
1065 {
1066         struct io_thread_req io_req;
1067         struct request *req;
1068         int err, n;
1069
1070         if(thread_fd == -1){
1071                 while((req = elv_next_request(q)) != NULL){
1072                         err = prepare_request(req, &io_req);
1073                         if(!err){
1074                                 do_io(&io_req);
1075                                 __ubd_finish(req, io_req.error);
1076                         }
1077                 }
1078         }
1079         else {
1080                 if(do_ubd || (req = elv_next_request(q)) == NULL)
1081                         return;
1082                 err = prepare_request(req, &io_req);
1083                 if(!err){
1084                         do_ubd = 1;
1085                         n = os_write_file(thread_fd, (char *) &io_req,
1086                                          sizeof(io_req));
1087                         if(n != sizeof(io_req))
1088                                 printk("write to io thread failed, "
1089                                        "errno = %d\n", -n);
1090                 }
1091         }
1092 }
1093
1094 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1095 {
1096         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1097
1098         geo->heads = 128;
1099         geo->sectors = 32;
1100         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1101         return 0;
1102 }
1103
1104 static int ubd_ioctl(struct inode * inode, struct file * file,
1105                      unsigned int cmd, unsigned long arg)
1106 {
1107         struct ubd *ubd_dev = inode->i_bdev->bd_disk->private_data;
1108         struct hd_driveid ubd_id = {
1109                 .cyls           = 0,
1110                 .heads          = 128,
1111                 .sectors        = 32,
1112         };
1113
1114         switch (cmd) {
1115                 struct cdrom_volctrl volume;
1116         case HDIO_GET_IDENTITY:
1117                 ubd_id.cyls = ubd_dev->size / (128 * 32 * 512);
1118                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1119                                  sizeof(ubd_id)))
1120                         return(-EFAULT);
1121                 return(0);
1122
1123         case CDROMVOLREAD:
1124                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1125                         return(-EFAULT);
1126                 volume.channel0 = 255;
1127                 volume.channel1 = 255;
1128                 volume.channel2 = 255;
1129                 volume.channel3 = 255;
1130                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1131                         return(-EFAULT);
1132                 return(0);
1133         }
1134         return(-EINVAL);
1135 }
1136
1137 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
1138 {
1139         struct uml_stat buf1, buf2;
1140         int err;
1141
1142         if(from_cmdline == NULL)
1143                 return 0;
1144         if(!strcmp(from_cmdline, from_cow))
1145                 return 0;
1146
1147         err = os_stat_file(from_cmdline, &buf1);
1148         if(err < 0){
1149                 printk("Couldn't stat '%s', err = %d\n", from_cmdline, -err);
1150                 return 0;
1151         }
1152         err = os_stat_file(from_cow, &buf2);
1153         if(err < 0){
1154                 printk("Couldn't stat '%s', err = %d\n", from_cow, -err);
1155                 return 1;
1156         }
1157         if((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
1158                 return 0;
1159
1160         printk("Backing file mismatch - \"%s\" requested,\n"
1161                "\"%s\" specified in COW header of \"%s\"\n",
1162                from_cmdline, from_cow, cow);
1163         return 1;
1164 }
1165
1166 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
1167 {
1168         unsigned long modtime;
1169         unsigned long long actual;
1170         int err;
1171
1172         err = os_file_modtime(file, &modtime);
1173         if(err < 0){
1174                 printk("Failed to get modification time of backing file "
1175                        "\"%s\", err = %d\n", file, -err);
1176                 return(err);
1177         }
1178
1179         err = os_file_size(file, &actual);
1180         if(err < 0){
1181                 printk("Failed to get size of backing file \"%s\", "
1182                        "err = %d\n", file, -err);
1183                 return(err);
1184         }
1185
1186         if(actual != size){
1187                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
1188                  * the typecast.*/
1189                 printk("Size mismatch (%llu vs %llu) of COW header vs backing "
1190                        "file\n", (unsigned long long) size, actual);
1191                 return(-EINVAL);
1192         }
1193         if(modtime != mtime){
1194                 printk("mtime mismatch (%ld vs %ld) of COW header vs backing "
1195                        "file\n", mtime, modtime);
1196                 return(-EINVAL);
1197         }
1198         return(0);
1199 }
1200
1201 int read_cow_bitmap(int fd, void *buf, int offset, int len)
1202 {
1203         int err;
1204
1205         err = os_seek_file(fd, offset);
1206         if(err < 0)
1207                 return(err);
1208
1209         err = os_read_file(fd, buf, len);
1210         if(err < 0)
1211                 return(err);
1212
1213         return(0);
1214 }
1215
1216 int open_ubd_file(char *file, struct openflags *openflags, int shared,
1217                   char **backing_file_out, int *bitmap_offset_out,
1218                   unsigned long *bitmap_len_out, int *data_offset_out,
1219                   int *create_cow_out)
1220 {
1221         time_t mtime;
1222         unsigned long long size;
1223         __u32 version, align;
1224         char *backing_file;
1225         int fd, err, sectorsize, asked_switch, mode = 0644;
1226
1227         fd = os_open_file(file, *openflags, mode);
1228         if (fd < 0) {
1229                 if ((fd == -ENOENT) && (create_cow_out != NULL))
1230                         *create_cow_out = 1;
1231                 if (!openflags->w ||
1232                    ((fd != -EROFS) && (fd != -EACCES)))
1233                         return fd;
1234                 openflags->w = 0;
1235                 fd = os_open_file(file, *openflags, mode);
1236                 if (fd < 0)
1237                         return fd;
1238         }
1239
1240         if(shared)
1241                 printk("Not locking \"%s\" on the host\n", file);
1242         else {
1243                 err = os_lock_file(fd, openflags->w);
1244                 if(err < 0){
1245                         printk("Failed to lock '%s', err = %d\n", file, -err);
1246                         goto out_close;
1247                 }
1248         }
1249
1250         /* Successful return case! */
1251         if(backing_file_out == NULL)
1252                 return(fd);
1253
1254         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
1255                               &size, &sectorsize, &align, bitmap_offset_out);
1256         if(err && (*backing_file_out != NULL)){
1257                 printk("Failed to read COW header from COW file \"%s\", "
1258                        "errno = %d\n", file, -err);
1259                 goto out_close;
1260         }
1261         if(err)
1262                 return(fd);
1263
1264         asked_switch = path_requires_switch(*backing_file_out, backing_file, file);
1265
1266         /* Allow switching only if no mismatch. */
1267         if (asked_switch && !backing_file_mismatch(*backing_file_out, size, mtime)) {
1268                 printk("Switching backing file to '%s'\n", *backing_file_out);
1269                 err = write_cow_header(file, fd, *backing_file_out,
1270                                        sectorsize, align, &size);
1271                 if (err) {
1272                         printk("Switch failed, errno = %d\n", -err);
1273                         goto out_close;
1274                 }
1275         } else {
1276                 *backing_file_out = backing_file;
1277                 err = backing_file_mismatch(*backing_file_out, size, mtime);
1278                 if (err)
1279                         goto out_close;
1280         }
1281
1282         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
1283                   bitmap_len_out, data_offset_out);
1284
1285         return fd;
1286  out_close:
1287         os_close_file(fd);
1288         return err;
1289 }
1290
1291 int create_cow_file(char *cow_file, char *backing_file, struct openflags flags,
1292                     int sectorsize, int alignment, int *bitmap_offset_out,
1293                     unsigned long *bitmap_len_out, int *data_offset_out)
1294 {
1295         int err, fd;
1296
1297         flags.c = 1;
1298         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
1299         if(fd < 0){
1300                 err = fd;
1301                 printk("Open of COW file '%s' failed, errno = %d\n", cow_file,
1302                        -err);
1303                 goto out;
1304         }
1305
1306         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
1307                             bitmap_offset_out, bitmap_len_out,
1308                             data_offset_out);
1309         if(!err)
1310                 return(fd);
1311         os_close_file(fd);
1312  out:
1313         return(err);
1314 }
1315
1316 static int update_bitmap(struct io_thread_req *req)
1317 {
1318         int n;
1319
1320         if(req->cow_offset == -1)
1321                 return(0);
1322
1323         n = os_seek_file(req->fds[1], req->cow_offset);
1324         if(n < 0){
1325                 printk("do_io - bitmap lseek failed : err = %d\n", -n);
1326                 return(1);
1327         }
1328
1329         n = os_write_file(req->fds[1], &req->bitmap_words,
1330                           sizeof(req->bitmap_words));
1331         if(n != sizeof(req->bitmap_words)){
1332                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1333                        req->fds[1]);
1334                 return(1);
1335         }
1336
1337         return(0);
1338 }
1339
1340 void do_io(struct io_thread_req *req)
1341 {
1342         char *buf;
1343         unsigned long len;
1344         int n, nsectors, start, end, bit;
1345         int err;
1346         __u64 off;
1347
1348         nsectors = req->length / req->sectorsize;
1349         start = 0;
1350         do {
1351                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1352                 end = start;
1353                 while((end < nsectors) &&
1354                       (ubd_test_bit(end, (unsigned char *)
1355                                     &req->sector_mask) == bit))
1356                         end++;
1357
1358                 off = req->offset + req->offsets[bit] +
1359                         start * req->sectorsize;
1360                 len = (end - start) * req->sectorsize;
1361                 buf = &req->buffer[start * req->sectorsize];
1362
1363                 err = os_seek_file(req->fds[bit], off);
1364                 if(err < 0){
1365                         printk("do_io - lseek failed : err = %d\n", -err);
1366                         req->error = 1;
1367                         return;
1368                 }
1369                 if(req->op == UBD_READ){
1370                         n = 0;
1371                         do {
1372                                 buf = &buf[n];
1373                                 len -= n;
1374                                 n = os_read_file(req->fds[bit], buf, len);
1375                                 if (n < 0) {
1376                                         printk("do_io - read failed, err = %d "
1377                                                "fd = %d\n", -n, req->fds[bit]);
1378                                         req->error = 1;
1379                                         return;
1380                                 }
1381                         } while((n < len) && (n != 0));
1382                         if (n < len) memset(&buf[n], 0, len - n);
1383                 } else {
1384                         n = os_write_file(req->fds[bit], buf, len);
1385                         if(n != len){
1386                                 printk("do_io - write failed err = %d "
1387                                        "fd = %d\n", -n, req->fds[bit]);
1388                                 req->error = 1;
1389                                 return;
1390                         }
1391                 }
1392
1393                 start = end;
1394         } while(start < nsectors);
1395
1396         req->error = update_bitmap(req);
1397 }
1398
1399 /* Changed in start_io_thread, which is serialized by being called only
1400  * from ubd_init, which is an initcall.
1401  */
1402 int kernel_fd = -1;
1403
1404 /* Only changed by the io thread. XXX: currently unused. */
1405 static int io_count = 0;
1406
1407 int io_thread(void *arg)
1408 {
1409         struct io_thread_req req;
1410         int n;
1411
1412         ignore_sigwinch_sig();
1413         while(1){
1414                 n = os_read_file(kernel_fd, &req, sizeof(req));
1415                 if(n != sizeof(req)){
1416                         if(n < 0)
1417                                 printk("io_thread - read failed, fd = %d, "
1418                                        "err = %d\n", kernel_fd, -n);
1419                         else {
1420                                 printk("io_thread - short read, fd = %d, "
1421                                        "length = %d\n", kernel_fd, n);
1422                         }
1423                         continue;
1424                 }
1425                 io_count++;
1426                 do_io(&req);
1427                 n = os_write_file(kernel_fd, &req, sizeof(req));
1428                 if(n != sizeof(req))
1429                         printk("io_thread - write failed, fd = %d, err = %d\n",
1430                                kernel_fd, -n);
1431         }
1432
1433         return 0;
1434 }